The F-actin filament capping protein CapG is a bona fide nucleolar protein.
Actin works in concert with myosin I to regulate the transcription of ribosomal genes in the nucleolus. Recently, nucleolar actin has been shown to be active in its polymeric form raising the question how actin dynamics is regulated in the nucleolus. Here, we show that the actin capping protein CapG localizes in the nucleolus of cultured cells. CapG transport to the nucleolus is an active and ATP-dependent process. Association of CapG with the nucleolus requires active RNA Polymerase I transcription. In addition, we show that activated Ran GTPase, an interaction partner of CapG, is also transported to the nucleolus. A constitutively active Ran mutant promotes CapG accumulation in the nucleolus indicating that CapG transport to the nucleolus can be supported by Ran. Our results suggest that filamentous actin in the nucleolus might be regulated by actin binding proteins such as CapG.
Hubert
Thomas
T
Department of Medical Protein Research, VIB, B-9000 Ghent, Belgium; Department of Biochemistry, Ghent University, Faculty of Medicine and Health Sciences, Albert Baertsoenkaai 3, B-9000 Ghent, Belgium.
Van Impe
Katrien
K
Department of Medical Protein Research, VIB, B-9000 Ghent, Belgium; Department of Biochemistry, Ghent University, Faculty of Medicine and Health Sciences, Albert Baertsoenkaai 3, B-9000 Ghent, Belgium.
Vandekerckhove
Joël
J
Department of Medical Protein Research, VIB, B-9000 Ghent, Belgium; Department of Biochemistry, Ghent University, Faculty of Medicine and Health Sciences, Albert Baertsoenkaai 3, B-9000 Ghent, Belgium.
Gettemans
Jan
J
Department of Medical Protein Research, VIB, B-9000 Ghent, Belgium; Department of Biochemistry, Ghent University, Faculty of Medicine and Health Sciences, Albert Baertsoenkaai 3, B-9000 Ghent, Belgium. Electronic address: jan.gettemans@ugent.be.
D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D002460:Cell Line; D002466:Cell Nucleolus / Q000378:metabolism*; D006801:Humans; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D012318:RNA Polymerase I / Q000378:metabolism; D020931:ran GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
D000199:Actins; D008840:Microfilament Proteins; D009687:Nuclear Proteins; C066575:CAPG protein, human; D012318:RNA Polymerase I; D020931:ran GTP-Binding Protein